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Resource centre > Linnaean names and their types: a permanent reference point

Linnaean names and their types: a permanent reference point

Volume 4 Number 1 - January 2007

Charlie Jarvis

It is essential for anyone studying and working with living organisms to know their correct scientific names. As Peter Raven of Missouri Botanical Garden (in Jarvis, 2007) writes, “Precise names are important because all of our food and most of our medicines come from plants, either directly or indirectly; the ecosystems that they dominate protect our topsoil and regulate our watersheds, determine local climate, and absorb greenhouse gases and other pollutants. Moreover, we are just beginning to understand plants properly at a molecular and cellular level, applications that demand precise ways of naming and understanding them.” In day-to-day life, using common or vernacular names to communicate about organisms can often work well enough between people who share the same language, and who are familiar with the same geographical area.

However, there can be pitfalls. Use of the name “bluebell” in the United Kingdom can, depending on area, risk confusing the blue-flowered bulbous plant of deciduous woods (Hyacinthoides non-scripta (L.) Rothm.) with the low-growing bellflower of open ground (Campanula rotundifolia L.). Horticulturally interesting groups of plants, too, provide scope for confusion, with the vernacular “geranium” referring to a member of the genus Pelargonium (not to the crane’s-bill genus, Geranium), and “veronica” used to indicate species belonging to the genus Hebe (rather than the speedwell genus, Veronica).

These problems are only compounded when many different languages are involved, over a wide geographical area. Hence the immense utility of the binomial naming system introduced for plants by the Swedish physician Carl Linnaeus (1707-1778) in 1753. Still in use today, it provides a fundamental framework for the scientific naming of plants. Consisting of a genus name (e.g. Ginkgo) and a species name (e.g. biloba) in Latin form, these binomials are used according to an internationally agreed set of rules which are laid out in the International Code of Botanical Nomenclature (ICBN) (McNeill & al. 2006). As McNeill & Turland write in the Preface to the ICBN, “Unambiguous names for organisms are essential for effective scientific communication; names can only be unambiguous if there are internationally accepted rules governing their formation and use”.

How binomials arose

Before Linnaeus’ introduction of binomials, organisms were given descriptive Latin names, which not only acted as a tag, but also described their features. These names were initially fairly brief, but, as more species became known, names became longer and more difficult to remember. For example, what was known as Arbutus folio serrato (Arbutus with saw-toothed leaves) in 1623 had become Arbutus caule erecto, foliis glabris serratis, baccis polyspermis (Arbutus with upright stems, hairless, saw-toothed leaves and many-seeded berries) 130 years later. Linnaeus’ corresponding binomial (now cited followed by an abbreviation of the author’s name, in this case “L.”) was Arbutus unedo L. This idea proved so simple and useful that others started to coin their own names for species they were describing for the first time. By the 1770s, most biologists had adopted them and the majority are still in use today. Linnaeus named more than 9,000 plants, including most major crop and medicinal plants and many commercially important ornamentals, as well as numerous common tropical species, and most of the common wild plants of Europe. His landmark work, Species Plantarum (1753), marks the starting point for the use of these names.

The Type Method

Linnaeus (1751) himself wrote in Philosophia Botanica, “If you do not know the names of things, the knowledge of them is lost too”. Today, stability in plant naming is established by what is known as the type method – when a new species is identified, a dried, pressed specimen of the plant, demonstrating its typical characters, is preserved and designated as the “type” of the name that is published for it. The type specimen provides a permanent reference point for everyone and establishes the name’s use. Any name can be checked against its type specimen, and if two names are found to apply to the same species, the earlier of them becomes the correct name to use. Although the type system developed gradually from the middle of the 19th century, it was not formally adopted in a Code of Botanical Nomenclature until 1930.

Linnaean Plant Name Typification Project, based at the Natural History Museum in London, has been working to establish type specimens retroactively for the 9,000 plant names of species (and a small number of varieties) coined by Linnaeus, so that the names can be correctly used. When the Project was set up in 1981, information on Linnaean typifications was widely scattered and it was not known how many names had been typified. Many choices (typifications) had been published piecemeal over the years, and in a wide variety of publications, so a major part of the Project’s work has involved making a huge literature search in order to draw this information together.

Linnaeus and his sources of information

Carl Linnaeus was a born encyclopaedist in an age that fostered and encouraged the methodical cataloguing of everything, from the organisms that make up the natural world to the listing and defining of words themselves – the 18th century saw the publication of the first dictionaries and encylopaedias. It was also a golden age of exploration – when James Cook departed on his epic voyage around the world in 1768, on board was the young Daniel Solander, a favourite pupil of Linnaeus. Inspired by Linnaeus’ teaching, many of his students (known as the “Apostles”) set off on journeys to America, to Egypt, to India and Japan, collecting plants and seeds to take back to the great master in Sweden.

Linnaeus’ own travels were more modest. He knew his native Sweden well, and lived in the Netherlands for three years, making short trips to Germany, Paris and England during that time. However, wherever he was, he continued to observe and list and describe everything he saw, not just plants but also mammals, birds, fishes and minerals, as well as people and their habits and customs. He also examined the herbaria of other collectors, such as the North American plants collected by John Clayton and in the possession of Linnaeus’ friend Johan Gronovius in Leiden, and the Ceylon collections made by Paul Hermann 70 years earlier. By 1746 Linnaeus had made a start on the work which is perhaps his most well-known, Species Plantarum. Then aged 39, he had been collecting plants and recording them all his life and had written guides to the floras of Lapland and Sweden as well as books on his philosophical approach to botany and accounts of the plants, native and nonnative, to be found on estates such as the Hartekamp in the Netherlands, home to the keen plantsman George Clifford, which contained such exotics as the banana.

In other words, when Linnaeus described and classified plants, he was drawing on a very wide range of sources of information, and his notion of what constituted a species could be very broad, taking in under a single name what we would regard today as a number of different species. Because the 18th-century Swede did not work according to our modern type concept, only very rarely can we be sure that he based his concept of a particular species on a single specimen (a “holotype”). For names other than these, it is necessary to choose a type (a “lectotype”) from among the specimens and illustrations that Linnaeus used in arriving at his concept of the species in question. A good comprehension of his working methods is essential for anyone undertaking the task of analyzing Linnaean names and designating types.

The literature survey revealed that around a quarter of all Linnaean names had been the subject of typification, but it was necessary to establish whether these type statements had been validly chosen, and where more than one type statement existed, which one should take priority. Before being accepted, each typification statement was carefully assessed. It was important to ensure that, for example, the chosen material was not collected after Linnaeus described the name (in which case it clearly could not have contributed to forming his concept of the species he was naming). For instance, in naming the the small tropical tree, Crescentia cujete L. (calabash) in 1753, Linnaeus used as his sources a number of published descriptions and illustrations from other authors (including one that is identifiable as an entirely different species, Amphitecna latifolia (Mill.) Gentry). However, Linnaeus could not have used the specimen (now in Linnaeus’ own herbarium at the Linnean Society of London (LINN)) that Gentry (1974: 831) chose as the lectotype. This is because the material is marked as having come from Patrick Browne (author of The Civil and Natural History of Jamaica, published in 1756) and we know from his letters that Linnaeus did not acquire Browne’s specimens until 1758, five years after Crescentia cujete was published. It follows that Browne’s specimen was not eligible to be selected as the lectotype, so the next choice (made by Wijnands 1983), of an illustration published by the English apothecary, Leonard Plukenet and cited by Linnaeus, is the lectotype of this name.

Designating new types

For the many names that, at the start of the Project, did not have a designated type, studies were made of the preserved specimens and illustrations that Linnaeus used. Working in close collaboration with many hundreds of specialists in different plant groups from around the world, we have designated type specimens for well over two thousand more of his names. In concentrating on some of the larger flowering plant groups (e.g. the families Apiaceae, Asteraceae, Boraginaceae, Brassicaceae, Caryophyllaceae, Convolvulaceae, Cyperaceae, Ericaceae, Fabaceae, Lamiaceae, Orchidaceae, Poaceae, Ranunculaceae and Rosaceae), type choices have been published by nearly 200 specialists from 34 different countries. In addition, because Linnaean binomials are also the earliest for plant groups such as the ferns and fernallies, liverworts, lichens, some algae and some fungi, we have also published detailed accounts of Linnaeus’ lichen (see Jørgensen et al. 1994) and algal (see Spencer et al. in press) names.

Linnaeus often drew his knowledge of species, particularly from tropical areas, from descriptions and illustrations (for specimens were simply unavailable). As a consequence, about 25 per cent of Linnaean names have illustrations as their lectotypes. They include, for example, threatened species such as Dracaena draco (L.) L. (dragon tree), Prunus lusitanicus L. subsp. lusitanicus (palo de loro), Cedrela odorata L. (Central American cedar) and Santalum album L. (sandalwood).

The majority, however, do have herbarium specimens as their types. Although many of these are found in Linnaeus’ own herbarium (LINN), e.g. Datisca cannabina L. (false hemp), Ginkgo biloba L. (maidenhair tree), Isoplexis (Digitalis) canariensis (L.) Loud. (cresto de gallo) and Drosera rotundifolia L. (round-leaved sundew), others can be found in additional herbaria that were studied by Linnaeus. Examples include the type of the nightflowering cactus, Selenicereus grandiflorus (L.) Britton & Rose in the herbarium of the Anglo-Dutch banker and plantsman, George Clifford, now at the Natural History Museum in London (BM), and those of Mandragora officinalis L. (mandrake) and Parnassia palustris L. (Grass of Parnassus), which are in Joachim Burser’s herbarium in Uppsala (UPS). Some, such as Epifagus virginiana (L.) W. Bart. (beechdrops) are in John Clayton’s herbarium of Virginian plants (BM), while others, e.g. Pavetta indica L. can be found in Paul Hermann’s Ceylon herbarium (BM).

Project Publications

Much of the information we have assembled during the Project is accessible online via the Natural History Museum website (http://www.nhm.ac.uk/researchcuration/ projects/linnaean-typification), and May 2007 will see the publication of a major book, Order out of Chaos, a comprehensive, 1,200 page guide to Linnaean Plant Names and their types. A co-publication between the Linnean Society of London and the Natural History Museum, this contains not only a detailed catalogue of all Linnaean binomials for plants, it also details Linnaeus’ own publications and those of other botanists that contributed to his understanding of plants. Significant plant collectors are enumerated, with examples of important specimens from Linnaeus’, and other, herbaria. Its publication coincides with the tercentenary of Linnaeus’ birth. A valuable contribution to the botanical literature, it will be of use to students, botanists, historians and conservationists worldwide, and another aid to nomenclatural stability. For further information, see Book notices and taxonomic resources.

Acknowledgements

The generous grant support of the Linnean Society of London to the Linnaean Plant Name Typification Project is gratefully acknowledged.